Solid-state lighting arrays are used for a number of lighting applications. For example, solid-state lighting panels including arrays of solid-state light emitting devices have been used as direct illumination sources in architectural and/or accent lighting. A solid-state light emitting device may include, for example, a packaged light emitting device including one or more light emitting diodes (LEDs), which may include inorganic LEDs, which may include semiconductor layers forming p-n junctions and/or organic LEDs (OLEDs), which may include organic light emission layers.
Solid-state lighting devices are often used in lighting fixtures, such as incandescent bulb replacement applications, task lighting, recessed light fixtures and the like. For example, Cree, Inc. produces a variety of light fixtures that use LEDs for illumination. The fixtures include can-type down lights, such as the LR-6 and CR-6, and troffer-type fixtures, such as the CR-24.
LEDs can be dimmed using, for example, linear dimming or pulse-width modulated (PWM) dimming. In a typical LED lighting apparatus, a microcontroller generates a PWM signal that is provided to a driver circuit that controls current passing through one or more LEDs. By varying the duty cycle of the PWM signal, the average current of the LEDs is proportionally changed, and the brightness of the LEDs varies accordingly.
Some conventional microcontroller-based dimming controllers implement linear dimming. Typically, the microcontroller samples a dimming control signal (e.g., from a commercial dimmer) and generates a PWM signal with its duty cycle varying with the dimming control signal. The PWM signal may be filtered with a low-pass filter, producing a DC voltage that is used to control a power stage of the driver circuit to adjust the LED current.